1. Field of the Invention
The present invention relates to a system using fuel comprising at least two combustible ingredients and more particularly, without limitation, to an internal combustion engine using fuel comprising acetylene and another combustible fuel.
2. Description of the Related Art
Acetylene is conventionally produced by reacting calcium carbide with water. The reaction is spontaneously occurring and can be conducted without any sophisticated equipment or apparatus. Such produced acetylene has been utilized for lighting in mine areas, by street vendors, etc. People often call such lighting sources “carbide lights” or “carbide lamps”. Industrial uses of acetylene as a fuel for motors or lighting sources, however, has been nearly nonexistent. In modern times, the use of acetylene as a fuel has been largely limited to acetylene torches for welding or welding-related applications. In most such applications, acetylene is generally handled in solution form, such as acetylene dissolved in acetone for example.
The clean burning nature of acetylene is self-evident from the stoichiometric equation:
 C2H2+2.5O2→2CO2+H2O
The reaction proceeds spontaneously at any temperature and pressure conditions and easily goes to completion without leaving any residues other than the desired combustion products, namely carbon dioxide and water. Further, the reaction ideally takes place in a gaseous phase without any need for catalytic assistance. The gas-phase reaction has several advantages over heterogeneous reactions such as gas-liquid, gas-solid, and solid-liquid reactions. For example, the gas-phase reaction does not require much effort for mixing necessary ingredients, assuring proper ratios, or handling by-products of combustion. Such advantages become very significant in fuel applications for combustion engines where liquid fuels such as gasoline have been conventionally used, and gasoline (liquid-phase) and air (gas-phase) interact contact in an engine for combustion reaction purposes.
Gas-phase reaction, however, involves different measures, controls, and safety precautions. If acetylene is used either in pure form or in concentrated form, there is a strong tendency for detonation, which directly contributes to the difficulty in preventing undesirable spontaneous chemical reaction.
Combustion reactions occurring at relatively low temperature conditions could provide several advantages, including the following:                1) Atmospheric nitrogen requires a relatively high temperature (T>1200° C.) to react with atmospheric oxygen in order to form nitrogen oxides (NOx) to any significant amount, the family of nitrogen oxides generally including N2O, NO, N2O3, NO2 and N2O5. Even at lower temperatures (T≅900° C.), small amounts of nitrogen oxides can be formed but only over extended periods of time. However, at such low temperatures, formation of NOx from reactions between nitrogen and oxygen are negligible or non-existent.        2) Low engine temperature alleviates any need for special emission control equipment commonly used in motor vehicles, such as an emission gas recirculation (“EGR”) valve for example. One of the primary functions of an EGR system in modern motor vehicles is to reduce the combustion temperature by recirculating a portion of exhaust gas into the intake manifold, thus achieving a reduction in NOx formation in the combustion chamber. Such a requirement is not needed in an engine operating under relatively low temperate conditions.        3) Low engine temperatures significantly reduce any substantial requirement for motor cooling. Cooling for an engine operating under relatively low temperature conditions can be readily accomplished either by air-cooling or by water cooling (including with ethylene glycol-water mixtures, propylene glycol-water mixtures, and the like), but with less stringent capacities than with engines operating at relatively high temperatures.        4) Low motor temperature and clean burning help and boost the fuel efficiency, since the combustion energy generated goes far less toward the maintenance of the engine temperature. In other words, the power produced per BTU generated by the fuel is greater in the case of acetylene than for other conventional fuels under the circumstances.        5) Low temperature combustion permits simpler and cheaper exhaust system design, such as shorter length for example, particularly when the combustion products consist only of carbon dioxide and water. In addition, the hardware for such an exhaust system could be physically smaller in size.        
Unfortunately, acetylene as a single fuel cannot be burned in an IC engine without severe knock and early ignition in the intake port, and in the cylinder, causing engine stopping and damage. For example, the results obtained from a computer model used to estimate the performance of a spark ignition engine when acetylene was used as a fuel was reported in “Computational Estimation of the Performance of a S. I. Engine with Various Fuels,” Nippon Kikai Gakkai Ronbunshu., B Hen., v. 56, n. 523, Mar. 190, pp. 830-835, by Katsumi Kataoka. Those calculations disclosed that when acetylene is used as a fuel, the flame temperatures rise high enough to cause the deterioration of the efficiency because of thermal dissociation, resulting in fairly high emissions of NO, especially with lean mixtures. In other words, these results appear to teach away from the use of acetylene as a fuel.
In another study reported in “Acetylene and Water as Fuels for Spark Ignition,” Proceedings of the Intersociety Energy Conversion Engineering Conference, published by IEEE, IEEE Service Center, Piscataway, New Jersey, v. 4, pp. 61-66, by F. Bassi et al., acetylene was utilized as a laboratory surrogate in order to test water injection as a means to control spark ignited combustion of highly detonating fuels. The acetylene-water mixture was sprayed directly into the manifold with a high pressure positive displacement pump. The results indicated that overall efficiencies were higher with acetylene-water fueling than with gasoline. In addition, injected water caused a sharp reduction of NOx emissions below that obtainable by means of exhaust gas recirculation (“EGR”).
Unfortunately, since water is not a combustible compound and is devoid of any BTU value for combustion purposes, injection of water into the combustion chamber decreases the effective volume available for gas expansion in the combustion chamber of the engine, thereby decreasing the horsepower output of the engine.
Thus, what is needed in a system for effectively and controllably utilizing acetylene, either as a mixture or concurrently with an alcohol or other combustible fluid, as a clean fuel for internal combustion engines wherein the combustible fluid can be used in conjunction with acetylene as an anti-knock and early ignition-preventing agent without reducing horsepower output arising from depletion of effective volume available for gas expansion due to the presence of a non-combustible fluid, such as water.